Me, that's why I originally posted it a few years ago. After a stint of sub-zero temperatures for several days, I began to notice that I was seeing a larger than normal difference in my Guru and dome thermometer on longer cooks. I checked the calibration of the dome thermometer in boiling water and it was significantly off. like 20F (if I remember right).
@jonj - I generally go with below freezing. It probably takes colder than that to mess with the calibration, but it's an easier metric to go by. So, in my case, I won't be leaving my thermometer in the KK until early May. Just becomes part of my routine; I take out the thermometer when I put the cover back on after I am sure the fire is out.